Therefore, our brain PI3K inhibitor must acquire both flexible and stable values of objects to guide each behavior. However, the flexible and stable values are often mutually conflicting (stability-flexibility

dilemma) (Abraham and Robins, 2005, Anderson, 2007, Daw et al., 2006 and Liljenström, 2003). For the flexible value, any short-term change in object value matters, and the memory must be updated quickly. For the stable value, only a long-term change matters, and the memory must be updated only slowly so that small changes can be ignored. It is still unclear how the brain encodes both flexible and stable values to guide choice behavior accordingly. It would be difficult for a single neural circuit to process the potentially conflicting values. One alternative hypothesis would be that the brain has two independent mechanisms, one encoding flexible memories and the other encoding stable memories to guide choice behavior differently in each situation. Notably, the parallel process has been suggested to be a fundamental feature of the brain anatomically and functionally (Alexander et al., 1986). Especially, the basal ganglia have well-known parallel anatomical circuits connected from cortical regions to output structures (Alexander et al., 1986, Kemp and Powell, 1970, Szabo, 1970 and Szabo, 1972). In Alpelisib cost particular, the caudate nucleus receives inputs from a large portion of the cerebral

cortex including the prefrontal and temporal cortex (Saint-Cyr et al., 1990, Selemon and Goldman-Rakic, 1985 and Yeterian and Van Hoesen, 1978), through which visual object information is processed 17-DMAG (Alvespimycin) HCl (Kim et al., 2012 and Yamamoto et al., 2012). We thus hypothesized that the caudate nucleus contains parallel functional units that process object value information independently. To test this hypothesis, we performed two experiments, first aiming at neuronal information processing and then behavioral causality. These experiments

together suggested that the head and tail of the primate caudate nucleus have distinct functions, the head guiding controlled behavior based on flexible values and the tail guiding automatic behavior based on stable values. To examine the value representation and the behavior control by the caudate nucleus, we used flexible and stable value procedures (Figure 1). Figure S1, available online, shows the underlying concept. In each case, the monkey experienced fractal objects with high values and low values. In the flexible value procedure (Figure S1A), objects changed their values frequently and the monkey had to adapt to the changes flexibly. This is a short-term learning process. In the stable value procedure (Figure S1B), objects retained their values (i.e., high or low) stably across repeated learning. This is a long-term learning process. The testing of the long-term memory was done in a separate experimental context in which objects were no longer associated with the previously assigned values.